Lightmapping question

I have created this function:

Function SwitchLightMap( Mesh, NewTexture )
	;this function changes the lightmap on a mesh to a selected lightmap
	Local SurfS=CountSurfaces( Mesh ) 
	Local SurfI=0
	
	For SurfI=1 To Surfs
		s=GetSurface( Mesh, SurfI ) 
		b=GetSurfaceBrush(s) 
		t0=GetBrushTexture( b, 0 ) 
		t1=GetBrushTexture( b, 1 )
		
		BrushTexture b, t0, 0, 0
		BrushTexture b, newtexture, 0, 1
		
		PaintSurface s, b
	Next 
End Function

I still get the same result tho, anyone have any ideas?